diff --git a/src/gsm_04_08.c b/src/gsm_04_08.c
new file mode 100644
index 0000000..4165b78
--- /dev/null
+++ b/src/gsm_04_08.c
@@ -0,0 +1,306 @@
+/* GSM Mobile Radio Interface Layer 3 messages on the A-bis interface 
+ * 3GPP TS 04.08 version 7.21.0 Release 1998 / ETSI TS 100 940 V7.21.0 */
+
+/* (C) 2008 by Harald Welte <laforge@gnumonks.org>
+ * All Rights Reserved
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ */
+
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+
+#include "msgb.h"
+#include "debug.h"
+#include "gsm_data.h"
+#include "gsm_subscriber.h"
+#include "gsm_04_08.h"
+
+#define GSM0408_ALLOC_SIZE	1024
+
+struct gsm_lai {
+	u_int16_t mcc;
+	u_int16_t mnc;
+	u_int16_t lac;
+};
+
+static void parse_lai(struct gsm_lai *lai, const struct gsm48_loc_area_id *lai48)
+{
+	u_int8_t dig[4];
+
+	/* MCC */
+	dig[1] = lai48->digits[0] & 0x0f;
+	dig[2] = lai48->digits[0] >> 4;
+	dig[3] = lai48->digits[1] & 0x0f;
+	lai->mcc = dig[3] * 100 + dig[2];
+
+	/* MNC */
+	dig[1] = lai48->digits[1] >> 4;
+	dig[2] = lai48->digits[2] & 0x0f;
+	dig[3] = lai48->digits[2] >> 4;
+	lai->mnc = dig[3] * 100 + dig[2];
+
+	lai->lac = lai48->lac;
+}
+
+static void to_bcd(u_int8_t *bcd, u_int16_t val)
+{
+	bcd[0] = val % 10;
+	val = val / 10;
+	bcd[1] = val % 10;
+	val = val / 10;
+	bcd[2] = val % 10;
+	val = val / 10;
+}
+
+static void generate_lai(struct gsm48_loc_area_id *lai48, u_int16_t mcc, 
+			 u_int16_t mnc, u_int16_t lac)
+{
+	u_int8_t bcd[3];
+
+	to_bcd(bcd, mcc);
+	lai48->digits[0] = bcd[0] | (bcd[1] << 4);
+	lai48->digits[1] = bcd[2];
+
+	to_bcd(bcd, mnc);
+	lai48->digits[2] |= bcd[2] << 4;
+	lai48->digits[3] = bcd[0] | (bcd[1] << 4);
+	
+	lai48->lac = lac;
+}
+
+#define TMSI_LEN	4
+#define MID_TMSI_LEN	(TMSI_LEN + 2)
+
+static void generate_mid_from_tmsi(u_int8_t *buf, u_int8_t *tmsi_bcd)
+{
+	buf[0] = MID_TMSI_LEN;
+	buf[1] = 0xf0 | GSM_MI_TYPE_TMSI;
+	buf[2] = tmsi_bcd[0];
+	buf[3] = tmsi_bcd[1];
+	buf[4] = tmsi_bcd[2];
+	buf[5] = tmsi_bcd[3];
+}
+
+static int gsm0408_sendmsg(struct msgb *msg)
+{
+	/* FIXME: set data pointer to beginning of L3 data object */
+
+	return rsl_data_request(msg);
+}
+
+static int gsm0408_rcv_cc(struct msgb *msg)
+{
+	struct gsm48_hdr *gh = msgb_l3(msg);
+
+	switch (gh->msg_type & 0xbf) {
+	case GSM48_MT_CC_CALL_CONF:
+		/* Response to SETUP */
+		DEBUGP(DCC, "CALL CONFIRM\n");
+		break;
+	case GSM48_MT_CC_RELEASE_COMPL:
+		DEBUGP(DCC, "RELEASE COMPLETE\n");
+		break;
+	case GSM48_MT_CC_ALERTING:
+		DEBUGP(DCC, "ALERTING\n");
+		break;
+	case GSM48_MT_CC_CONNECT:
+		DEBUGP(DCC, "CONNECT\n");
+		/* need to respond with CONNECT_ACK */
+		break;
+	case GSM48_MT_CC_RELEASE:
+		DEBUGP(DCC, "RELEASE\n");
+		/* need to respond with RELEASE_COMPLETE */
+		break;
+	case GSM48_MT_CC_EMERG_SETUP:
+		//DEBUGP(DCC, "EMERGENCY SETUP\n");
+	case GSM48_MT_CC_SETUP:
+		//DEBUGP(DCC, "SETUP\n");
+		/* FIXME: continue with CALL_PROCEEDING, ALERTING, CONNECT, RELEASE_COMPLETE */
+	default:
+		fprintf(stderr, "Unimplemented GSM 04.08 msg type 0x%02x\n",
+			gh->msg_type);
+		break;
+	}
+}
+
+/* Chapter 9.2.14 : Send LOCATION UPDATE REJECT */
+int gsm0408_loc_upd_rej(struct gsm_bts_link *bts_link, u_int8_t cause)
+{
+	struct msgb *msg = msgb_alloc(GSM0408_ALLOC_SIZE);
+	struct gsm48_hdr *gh;
+	
+	msg->bts_link = bts_link;
+
+	gh = (struct gsm48_hdr *) msgb_put(msg, sizeof(*gh) + 1);
+	gh->proto_discr = GSM48_PDISC_MM;
+	gh->msg_type = GSM48_MT_MM_LOC_UPD_ACCEPT;
+	gh->data[0] = cause;
+
+	DEBUGP(DMM, "-> LOCATION UPDATE REJECT\n");
+
+	return gsm0408_sendmsg(msg);
+}
+
+/* Chapter 9.2.13 : Send LOCATION UPDATE ACCEPT */
+int gsm0408_loc_upd_acc(struct gsm_bts_link *bts_link, u_int8_t *tmsi)
+{
+	struct gsm_bts *bts = bts_link->bts;
+	struct msgb *msg = msgb_alloc(GSM0408_ALLOC_SIZE);
+	struct gsm48_hdr *gh;
+	struct gsm48_loc_area_id *lai;
+	u_int8_t *mid;
+	
+	msg->bts_link = bts_link;
+
+	gh = (struct gsm48_hdr *) msgb_put(msg, sizeof(*gh));
+	gh->proto_discr = GSM48_PDISC_MM;
+	gh->msg_type = GSM48_MT_MM_LOC_UPD_ACCEPT;
+
+	lai = (struct gsm48_loc_area_id *) msgb_put(msg, sizeof(*lai));
+	generate_lai(lai, bts->network->country_code,
+		     bts->network->network_code, bts->location_area_code);
+
+	mid = msgb_put(msg, MID_TMSI_LEN);
+	generate_mid_from_tmsi(mid, tmsi);
+
+	DEBUGP(DMM, "-> LOCATION UPDATE ACCEPT\n");
+
+	return gsm0408_sendmsg(msg);
+}
+
+
+/* Chapter 9.2.15 */
+static int mm_loc_upd_req(struct msgb *msg)
+{
+	struct gsm_bts *bts = msg->bts_link->bts;
+	struct gsm48_loc_upd_req *lu;
+	struct gsm_subscriber *subscr;
+
+	u_int8_t mi_type = lu->mi[0] & GSM_MI_TYPE_MASK;
+
+	switch (mi_type) {
+	case GSM_MI_TYPE_IMSI:
+		/* look up subscriber based on IMSI */
+		subscr = subscr_get_by_imsi(&lu->mi[1]);
+		break;	
+	case GSM_MI_TYPE_TMSI:
+		/* look up the subscriber based on TMSI, request IMSI if it fails */
+		subscr = subscr_get_by_tmsi(&lu->mi[1]);
+		if (!subscr) {
+			/* FIXME: send IDENTITY REQUEST message to get IMSI */
+			//gsm0408_identity_request(...GSM_MI_TYPE_IMSI);
+		}
+		break;
+	case GSM_MI_TYPE_IMEI:
+	case GSM_MI_TYPE_IMEISV:
+		/* no sim card... FIXME: what to do ? */
+		fprintf(stderr, "Unimplemented mobile identity type\n");
+		break;
+	default:	
+		fprintf(stderr, "Unknown mobile identity type\n");
+		break;
+	}
+
+	if (!subscr) {
+		/* 0x16 is congestion */
+		gsm0408_loc_upd_rej(msg->bts_link, 0x16);
+		return -EINVAL;
+	}
+
+	subscr_update(subscr, bts);
+	return gsm0408_loc_upd_acc(msg->bts_link, subscr->tmsi);
+}
+
+static int gsm0408_rcv_mm(struct msgb *msg)
+{
+	struct gsm48_hdr *gh = msgb_l3(msg);
+	int rc;
+
+	switch (gh->msg_type & 0xbf) {
+	case GSM48_MT_MM_LOC_UPD_REQUEST:
+		DEBUGP(DMM, "LOCATION UPDATE REQUEST\n");
+		rc = mm_loc_upd_req(msg);
+		break;
+	case GSM48_MT_MM_ID_RESP:
+	case GSM48_MT_MM_TMSI_REALL_COMPL:
+	case GSM48_MT_MM_AUTH_RESP:
+	case GSM48_MT_MM_IMSI_DETACH_IND:
+	case GSM48_MT_MM_CM_SERV_REQ:
+	case GSM48_MT_MM_CM_REEST_REQ:
+		fprintf(stderr, "Unimplemented GSM 04.08 MM msg type 0x%02x\n",
+			gh->msg_type);
+		break;
+	default:
+		fprintf(stderr, "Unknown GSM 04.08 MM msg type 0x%02x\n",
+			gh->msg_type);
+		break;
+	}
+
+	return rc;
+}
+static int gsm0408_rcv_rr(struct msgb *msg)
+{
+	struct gsm48_hdr *gh = msgb_l3(msg);
+
+	switch (gh->msg_type) {
+	case GSM48_MT_RR_CLSM_CHG:
+		DEBUGP(DRR, "CLASSMARK CHANGE\n");
+		/* FIXME: what to do ?!? */
+		break;
+	case GSM48_MT_RR_PAG_RESP:
+	default:
+		fprintf(stderr, "Unimplemented GSM 04.08 msg type 0x%02x\n",
+			gh->msg_type);
+		break;
+	}
+
+	return 0;
+}
+
+/* here we pass in a msgb from the RSL->RLL.  We expect the l3 pointer to be set */
+int gsm0408_rcvmsg(struct msgb *msg)
+{
+	struct gsm48_hdr *gh = msgb_l3(msg);
+	u_int8_t pdisc = gh->proto_discr & 0x0f;
+	int rc;
+	
+	switch (pdisc) {
+	case GSM48_PDISC_CC:
+		rc = gsm0408_rcv_cc(msg);
+		break;
+	case GSM48_PDISC_MM:
+		rc = gsm0408_rcv_mm(msg);
+		break;
+	case GSM48_PDISC_RR:
+		rc = gsm0408_rcv_rr(msg);
+		break;
+	case GSM48_PDISC_MM_GPRS:
+	case GSM48_PDISC_SM:
+		fprintf(stderr, "Unimplemented GSM 04.08 discriminator 0x%02d\n",
+			pdisc);
+		break;
+	default:
+		fprintf(stderr, "Unknown GSM 04.08 discriminator 0x%02d\n",
+			pdisc);
+		break;
+	}
+
+	return rc;
+}